Treatment of process gases, e.g., flue gases, that include pollutants, such as, sulfur oxides, hydrogen sulfide, and mercury, is essential since these pollutants act as precursors to acid rain and photochemical smog. The content of sulfur dioxide in flue gases, for example, varies over a wide range and can be relatively low, such as 1-3%, or sometimes as high as 20%. Although the mercury content of flue gas is typically very low, given its high toxicity, environmental specifications require the complete removal of mercury. Therefore, there is a need in the art to provide a cost effective process to reduce emitted pollutants, such as, sulfur oxides, hydrogen sulfide and mercury. In addition, treatment processes must be able to effectively treat a large volume of gas to reduce contaminant levels below environmental specifications.
U.S. Pat. No. 6,737,031 provides a method of simultaneously reducing carbon dioxide emissions and sulfur dioxide emissions produced by the combustion of carbon-containing matter in a hearth. The method consists of injecting a calcium-based agent, e.g., calcium oxide, into a hearth to absorb SO2, then using the fraction of the calcium-based agent that has not reacted with SO2 to capture CO2 by carbonization.
U.S. Pat. No. 6,534,024 discloses an exhaust gas treatment process in which exhaust gas containing mercury and sulfur dioxide is subjected to a desulfurization treatment in a desulfurizing absorption tower and then passed through a mist eliminator for removing mercury from the desulfurized exhaust.
U.S. Pat. No. 4,557,912 discloses a method of treating air-polluting waste containing sulfur dioxide by removing solid particulate matter, separating the waste industrial flue gases into high and low molecular weight fractions, in which the higher molecular weight fraction contains a greater concentration of sulfur dioxide, and oxidizing the sulfur dioxide by contacting it with oxygen and a variety of nitrogen oxides.
U.S. Pat. No. 5,976,373 relates to a process and system for the removal of hydrogen sulfide from an anaerobic digester effluent gas stream. The method comprises adding oxygen to the effluent gas stream to form an oxygen-enriched gas stream; removing particulates, including water and bacteria, from the gas stream; and removing hydrogen sulfide via the Claus reaction to form a hydrogen sulfide-free gas stream, which is suitable for use as a fuel gas source in a power plant.
U.S. Pat. No. 5,407,466 discloses a process for treating gas streams containing hydrogen sulfide, carbon dioxide, water vapor and methane using a membrane separation process.
U.S. Pat. No. 5,147,620 discloses a process for removing hydrogen sulfide from gas streams by passing the gas stream through an aqueous solution of copper (II) ions to convert the hydrogen sulfide to copper sulfide. The copper (II) ion solution is prepared by admixing powdered copper (Cu) with an aqueous solution of nitric acid. The copper (II) ion solution may be regenerated from the copper sulfide by treatment with nitric acid.
U.S. Pat. No. 6,878,358 discloses a process for removing mercury from flue gases of a furnace by feeding bromine, or a bromine compound, to the furnace or the flue gas of the furnace. The temperature during the process is at least 500 C., which causes combustion or incineration of any sulfur compounds. The flue gas is then subjected to a wet cleanup to remove mercury.
U.S. Pat. No. 6,638,347 discloses a carbon-based powder containing cupric chloride for removing mercury from a high temperature, high moisture gas stream.
WO 2000062906 describes a process to remove mercury from waste gases using oxide of metals, such as Au, Ag, Cu, Sn etc., to form an amalgam with mercury.
However, previous techniques for the reduction of pollutants from a gas are not sufficiently effective and typically have high capital and operating costs. Accordingly, there is a need in the art to provide an effective process to reduce pollutants, such as carbon dioxide, mercury, sulfur compounds, nitrogen compounds and carbon compounds, that are produced during industrial applications.